A starter for the internal combustion engine of a two-wheeled motor vehicle is shown in FIG. 1 to illustrate a conventionally known internal combustion engine starter of the type to which this invention pertains. The engine has a crankshaft 1 to which a sprocket 2 is secured. An intermediate shaft 3 lies in parallel to the crankshaft 1 and is rotatably supported by a bearing 4 on a stationary member not shown. A sprocket 5 is connected to the intermediate shaft 3 by a rotational variation buffering mechanism not shown. The sprocket 5 is connected to the sprocket 2 by a chain 6.
An overrunning clutch 7 has an outer member 7a to which the sprocket 5 is secured, and an inner member 7b fitted about the intermediate shaft 3. A sleeve 8 is disposed between the shaft 3 and the inner member 7b which are rotatable relative to each other. A spur gear 7c is formed on the inner member 7b. A spur gear 9 is secured to the intermediate shaft 3. A large gear 10 meshes with the spur gear 9 and is connected to a speed change gear not shown by a clutch not shown. An intermediate gear 11 is secured to a rotary shaft 12 and meshes with the spur gear 7c. A self-starting motor 13, which is driven by a battery 15 upon closure of a self-starting switch 14, has an output shaft 13a on which a pinion 16 meshing with the intermediate gear 11 is secured. A lever shaft 17 has at one end a clutch portion 17a which engages it unidirectionally with the rotary shaft 12. A kick lever 18 is connected to the other end of the lever shaft 17. The sprockets 2 and 5, chain 6, overrunning clutch 7, intermediate gear 11, rotary shaft 12, pinion 16, self-starting motor 13, self-starting switch 14 and battery 15 form a first cranking mechanism. The sprockets 2 and 5, chain 6, overrunning clutch 7, intermediate gear 11, rotary shaft 12, lever shaft 17 and kick lever 18 form a second cranking mechanism which is manually operable.
The manual cranking mechanism makes it possible to start the engine mechanically as will hereinafter be described. The kick lever 18 is actuated to rotate the lever shaft 17 and its rotation is transmitted to the crankshaft 1 through the rotary shaft 12, intermediate gear 11, overrunning clutch 7, sprocket 5, chain 6 and sprocket 2, whereby the engine is started. The rotation of the engine is transmitted to the speed change gear through the sprocket 2, chain 6, sprocket 5, rotational variation buffering mechanism, intermediate shaft 3, spur gear 9, large gear 10 and the clutch not shown. The overrunning clutch 7 prevents the reverse motion of the kick lever 18, etc.
The cranking mechanism including the self-starting motor 13 enables the electrical starting of the engine as will hereinafter be described. The self-starting switch 14 is closed to supply electric current from the battery 15 to the self-starting motor 13 and thereby cause it to rotate. The rotation of the output shaft 13a is transmitted to the crankshaft 1 through the pinion 16, intermediate gear 11, overrunning clutch 7, sprocket 5, chain 6 and sprocket 2, whereby the engine is started. The unidirectional engagement of the clutch portion 17a prevents the reverse rotation of the kick lever 18 and the lever shaft 17. The rotation of the engine is transmitted to the speed change gear as hereinabove described.
The kick lever 18 and the lever shaft 17 have, however, their own structural limitations which disable them to rotate beyond a certain angle to cause the crankshaft 1 to rotate continuously. An internal combustion engine having a large displacement capacity is particularly difficult to start by the cranking mechanism including the kick lever 18. The cranking mechanism including the kick lever 18 and the cranking mechanism including the self-starting motor 13 are, therefore, both provided for some internal combustion engines of large displacement capacity for two-wheeled motor vehicles, as shown in FIG. 1. A high torque is required for causing the crankshaft 1 to rotate, especially when starting its rotation. The battery 15 in a two-wheeled motor vehicle has a relatively small capacity due to a limited space available for its installation. It is rapidly consumed, since it is freuquently used to start the engine. A reduction in the voltage supplied from the battery makes it more difficult to start the engine quickly.